This invention relates generally to a novel audiometric device.
More particularly, this invention concerns an apparatus useful in performing contralateral testing of intraaural muscle reflex. Whereas a wide variety of audiometric tests may be conducted with the apparatus of the present invention, the apparatus will find particular utility in rapid sequenced contralateral testing of intraaural muscle reflex.
In the past it has been useful for a physician or audiologist to measure various acoustic parameters of a patient's ear in order to diagnose ear malfunctions. Inasmuch as many ear malfunctions occur in the middle ear and cannot be observed directly by the physician or audiologist, different tests must be performed in order to isolate and identify the most probable cause of a hearing or ear malfunction.
Because of the relatively small dimensions and location of the critical hearing components of the ear, the testing procedures must necessarily be conducted with a minimum of error. In addition, the testing procedure desirably imposes minimal discomfort on the patient being tested. This latter aspect needs attention lest people are discouraged from submitting to such testing voluntarily.
In accoustic impedance audiometry, a contralateral testing method has been established as an indicator of hearing function. In this test, the external auditory meatus or canal of one ear is penetrated by a probe. This probe is then sealed off from the ambient atmosphere to isolate a volume lying between the probe tip and the tympanic membrane or eardrum. By controlling the pressure within this isolated volume, the eardrum may be manipulated to a neutral position. In this position of the eardrum, a known condition is achieved in the stapedius muscle and in the tensor-tympani muscle. In normal cases, the eardrum is a compliant condition in a neutral position.
As this test has been conducted in the prior art, the opposite ear is covered with an audiometric headset of the type disclosed in the U.S. Pat. No. 3,220,505 to Hargrave in order to present a closely controlled sound stimulus to that other ear. When the other ear is stimulated with sound, a response occurs in the probed ear. This response is in the nature of muscle reflex of the stapedius muscle, and, in some cases, of the tensor-tympani muscle, and this reflex results in a movement of the eardrum. This movement of the eardrum may be detected as a pressure change or as a geometric change in the probed ear. This intraaural muscle reflex which occurs in one ear as a result of a stimulus in the other ear occurs by virtue of a phenomenon of neural crossover. This reflex is useful to a physician or audiologist in determining hearing functions particularly in patients who are unable to communicate to the examiner the presence of an audible tone, e.g., infants or handicapped persons.
The probe tip and headset utilized in tests in the past are required to be very carefully positioned with respect to the patient's ears. This careful placement is necessitated by the precise nature of the examination. The positioning of this equipment may be extremely time consuming and, hence, limit the number of patients which may be examined by a physician or audiologist in a given time period. Moreover, it will be appreciated that when it is desired to test the intraaural muscle reflex of the other ear, the equipment must be reversed. That is, the probe must be removed from the first ear and repositioned in the second ear, and the headset must be positioned on the opposite ear.
Of related significance is the ease with which a probe may be inserted and held in position in the auditory canal of a patient. It will, of course, be appreciated that in the performance of various audiological tests, the probe tip must be sealed in such a manner as to permit the isolation of a volume between the probe tip and the ear drum. In the past, earplugs and ear probes have been available with a flexible, expandable bag or bladder adapted for expansion within the auditory canal of the ear. After the probe has been inserted into the auditory canal to a desired depth, the bladder of the expandable bag is inflated or pressurized. Such probe tips represent a relatively fast way of sealing a probe in an auditory canal. However, inasmuch as these probe tips must be cleaned between use, it has been found that the bladders do not inflate satisfactorily or give as desirable a seal after repeated cleanings.
Recognizing the need for an improved audiometric device for contralateral intraaural muscle reflex testing, it would therefore be desirable to provide an audiometric apparatus which eliminates the necessity of moving the testing apparatus from one ear to another and wherein such apparatus provides quick sealing ear probe tips which are readily replaceable and sufficiently inexpensive in cost to be disposed of after use.